Essential or so-called idiopathic microscopic hematuria remains an unsolved problem for urologists and nephrologists, despite improvements in diagnostic methods. The problem, quite often, is that a patient is determined to have some blood cells in his urine. When this occurs, especially if they are small in number, it is difficult to know whether the same originate in the upper or the lower urinary tract. For this reason, sometimes a patient although he has blood in the urine in small quantities is told to return after a set period of time for further checking. With this invention it is possible to determine the area of the urinary tract affected which is an important first step in making a diagnosis. It is a purpose, therefore, of this invention to provide a catheter which is useful in making such a diagnosis.